1. Field of the Invention
The invention relates to a medical guide wire which is therapeutically arranged to retractably move against a tip of a puncture needle set in advance into an arteria carotis interna in a remedial method (venipuncture) to insert a central venous catheter into the arteria carotis interna.
2. Description of Related Art
Upon implementing the venipuncture to insert a central venous catheter into the arteria carotis interna, an insertion tool for a medical guide wire has been used to unerringly insure the insertion safely against the arteria carotis interna with a simple procedure as represented by Japanese Laid-open Patent Application No. 10-118192 (referred to simply as “first reference” hereinafter).
The insertion tool for the medical guide wire has a puncture needle and a side support member which are to be removably attached to a syringe cylinder. The puncture needle is manipulated beforehand to puncture the needle tip into an appropriate point of the venous vessel, and then, the medical guide wire is inserted into the venous vessel through the side support member.
In the meanwhile, the medical guide wire (abbreviated as “the guide wire” hereinafter) is inserted into a tortuous and thin vascular vessel to introduce a distal end of the guide wire into a diseased lesion by manipulating (push-pull and turn) a band access portion placed outside a subject patient.
In order to achieve a smooth manipulation when inserting the guide wire into the vascular vessel, it is required for the guide wire to have certain multi-mechanical properties. The multi-mechanical properties include a high flexibility, a good straightness in an unrestricted free state and a good restitutivity from the deformed configuration. The guide wire of this type is required at its distal end portion to have a high flexibility, while at the sane time, required at its rear portion to have an appropriate rigidity as a functionally gradient property. It is also indispensable for the distal end to have a high maneuverability in which the distal end properly responds to the manipulation which is to be done at the hand access portion outside the subject patient.
The guide wire is generally formed by winding a single one wire (not stranded wires but an ordinary single line wire) into a hollow tube structure in which an elongated core is inserted. Both end portions of the hollow tube structure are fixed to the elongated core by means of soldering procedure.
Upon inserting the central venous catheter into the arteria carolis interna, the puncture needle 5a is set into the arteria carotis interna near a common carotid artery as shown in FIG. 14. The needle tip 6a has a rake surface end sharpened by cutting the puncture needle 5a with two-stop angles (θ2, θ3) against its axial direction (e.g., θ2=18−22 degrees). In order to precisely puncture the arteria carotis interna which is diametrically smaller than a maximum breadth of the rake surface end of the needle tip 6a, it is necessary for the manipulator to suppress the blood vessel T with his or her fingers to inflate it as shown at the phantom line in FIG. 14 until the manipulator feels the blood regurgitation to confirm that the punctured position is appropriate.
Thereafter, as shown FIGS. 14, 15 and 16, the guide wire 20a is inserted into the puncture needle 5a through the side support member (not shown). Then, the puncture needle 5a is pulled from the blood vessel T to inserted the central venous catheter (not shown) into the guide wire 20a. This manipulation requires highly skilled techniques so that the manipulator would often have to repeat the pull and puncture procedure several times until he or she gets accustomed to appropriately puncture in the venipuncture procedure.
Meanwhile, the distal end of the guide wire 20a has a preshaped portion (P) plastically deformed into a U-shaped or dog-legged configuration by a finger tip operation in order to smoothly insert the guide wire 20a into the blood vessel T. For this reason, upon inserting the guide wire 20a through the needle tip 6a, the preshaped portion (P) causes the guide wire 20a to bend upward with the needle tip 6a and the vascular wall as fulcra.
Since the guide wire 20a is formed by winding the single one wire into helical coil structure, the pull operation against the guide wire 20a likely causes to induce a helical clearance between the wire coil elements 21a of the helical coil structure. When the guide wire 20a is manipulatively bent, the bending force against the guide wire 20a also likely causes to induce clearance between the wire coil elements 21a of the helical coil structure, as is often the case with a general helical spring which is likely to apear the clearance between the wire coil elements when pulled in the lengthwise direction 4a. This often makes the needle tip 6a hitch its edge portion 7a in the wire coil elements 21a upon insertably slide the guide wire 20a into the puncture needle 5a. 
In the situation in which the guide wire 20a is deformed upward into a bow-shaped configuration within the puncture needle 5a so as to appear a minute clearance between the wire coil elements 21a, the pulling operation against the guide wire 20a increases the minute clearance to make the wire coil elements 21a likely hitch in knife edge ends 7A, 7B of the edge portion 7a due to the sliding resistance against the puncture needle 5a as shown in FIGS. 15 and 16. The hitching incident against the knife edge ends 7A, 7B occasions the guide wire 20a to retract inside the rake surface end of the edge portion 7a to likely engage it with an inner surface of the puncture needle 5a. 
In this instance, the wire coil elements 21a of the guide wire 20a generally forms an angle (θ5) in the range of 78 to 82 degrees against an axial direction 4a of the puncture needle 5a. 
When forcibly pulling the guide wire 20a from the puncture needle 5a with the edge portion 7a hitched in the wire coil elements 12a, the pulling force likely causes the guide wire 20a to rupture its thin single wire coil structure. The pulling force also induces a reactional twitch against the puncture needle 5a to make it mistakenly pierce into the common carotid artery near the blood vessel (arteria carotis interna) T so as to invite complications all the more difficult to cure.
Therefore, it is an object of the invention to overcome the above drawbacks, and provide a medical guide wire which is capable of eliminating a possibility to hitch a puncture needle in wire coil elements of the guide wire so as to smoothly insert into and pull from the puncture needle to resultantly improve the curability significantly against the diseased area.